Technical Field
The present invention relates to a semiconductor light-emitting device which has a light-emitting element module that connects a plurality of serially connected light-emitting elements in parallel, in particular, to a technology which suppresses the heat generation of a transistor that controls currents of the light-emitting elements.
Related Art
In a semiconductor laser device recited in patent literature 1, a plurality of serially connected laser diodes are further connected in a plurality of columns in parallel, anodes of the plurality of columns of laser diodes are collectively connected, and cathodes of the plurality of columns of laser diodes are collectively connected to configure a plurality of parallel lines. In this way, currents can be provided to each laser diode by one current control element. Therefore, the semiconductor laser device can be realized with a simple configuration.
However, potential differences of the plurality of laser diodes on each parallel line are the same, but a forward voltage of each laser diode has individual difference. Therefore, the currents flowing through the plurality of laser diodes on each parallel line are different, so that the currents would concentrate in any one of the parallel lines. As a result, the service life of the laser diodes where the currents concentrate becomes short.
In addition, in a semiconductor laser device recited in patent literature 2, a plurality of serially connected laser diodes (lines) are provided in a plurality of columns, one of the ends from each of the plurality of columns of lines is collectively connected, current control elements are connected to the plurality of columns of lines at the other end, and the current in each line is controlled by each current control element. On this occasion, if the number of the laser diodes on each line is set to be the same, the heat generation of the current control elements becomes great due to a forward voltage difference of the laser diode in each line.
In addition, patent literatures 3, 4 are known as conventional literature.